Herpes Complicates Schizophrenia

Action Points

Explain to interested patients that this study suggests that herpes simplex 1 might play a role in the cognitive deficits experienced by patients with schizophrenia.

In a small cohort study of schizophrenia patients, exposure to herpes simplex 1 was associated with worse scores on a range of cognitive tests, according to David Schretlen, PhD, of the Johns Hopkins University School of Medicine, and colleagues.

Patients with serum antibodies to the virus also had reduced gray matter volume in the anterior cingulate and parts of the cerebellum -- areas of the brain linked to executive functioning and psychomotor speed, Schretlen and colleagues reported in the May issue of Schizophrenia Research.

Moreover, "the most novel and potentially important finding," the researchers said, is that poor cognitive test results correlated with the reductions in brain volume that distinguished between patients exposed to the virus and those not exposed.

"We're finding that some portion of cognitive impairment usually blamed solely on the disease of schizophrenia might actually be a combination of schizophrenia and prior exposure to herpes simplex virus 1 infection, which reproduces in the brain," Schretlen said in a statement.

One clinical implication is that "it might be possible to reduce the risk or the extent of cognitive deficits" by the use of antiviral drugs, if patients exposed to the virus can be identified early, he said.

Cognitive impairment, including problems with psychomotor speed, concentration, learning, and memory, are important symptoms of schizophrenia, and may appear well before traditional symptoms such as delusions or hallucinations.

And previous research has shown that schizophrenic patients with antibodies to herpes are likely to have more severe cognitive deficits than those without, while other studies have shown that exposure to the virus is linked to reduction in gray matter volume.

But, the researchers said, it has not been clear if the cognitive deficits are directly related to the decreased brain volume.

To help clarify the issue, they analyzed data from 40 schizophrenic patients from two Baltimore hospitals, 25 of whom had antibodies to the virus.

The researchers also used magnetic resonance imaging to assess brain volume differences between the two groups.

Analysis showed the herpes-exposed patients did worse on all the cognitive tests than their non-exposed counterparts, although the differences reached significance on only two measures.

Specifically, exposed patients did worse on the tests for psychomotor speed and verbal memory. Both differences were significant at P<0.027 after correction for repeated measurements.

Schretlen and colleagues also found that, among herpes-exposed patients, MRI scans showed decreased gray matter volume in regions including the right cingulate gyrus BA 32, the right cerebellar fastigium, the left thalamus, and the right pallidus.

A multiple regression analysis showed that poor performance in the Trail Making Test of psychomotor speed was correlated with decreased gray matter volume in the bilateral cingulate gyrus, the right anterior cingulate, and the right parahippocampal gyrus, as well as in the occipital lobe and cerebellum bilaterally -- all at P<0.001.

Because herpes replicates in the brain it is possible the virus is directly causing the cognitive deficits by attacking these brain regions, Schretlen said.

The researchers noted that the study had two main limitations: It might have been too small to detect some important gray matter abnormalities, especially in the temporal lobes, and it's not possible to say whether herpes status alone accounts for the observed differences in cognitive functioning and brain structure.

The study was supported by the Stanley Medical Research Institute.

Schretlen reported getting royalties from sales of the Brief Test of Attention. No other potential conflicts were reported.

Accessibility Statement

At MedPage Today, we are committed to ensuring that individuals with disabilities can access all of the content offered by MedPage Today through our website and other properties. If you are having trouble accessing www.medpagetoday.com, MedPageToday's mobile apps, please email legal@ziffdavis.com for assistance. Please put "ADA Inquiry" in the subject line of your email.